When a conventional electrical contactor or relay is energized, a movable metallic armature is drawn towards a magnetic core such that electrical contacts mechanically linked to the armature are bought into or moved out of contact with electrical contacts disposed on the housing of the contactor, thus closing or opening an electrical circuit. Because the movable armature will have some momentum remaining after the contacts make or break, and to assure good separation or firm engagement of the contacts, the movable armature is allowed to continue to move towards the magnetic core. This movement of the armature will substantially cease when the armature collides with a stationary portion of the contactor, such as the magnetic core.
After contacting the magnetic core, the armature will move away or rebound from the magnetic core. The armature will continue to rebound until such time as the forces acting on the armature cause it to reverse direction for a second time, whereupon the cycle starts anew. This cycle of attraction, collision, and rebound will continue until the kinetic energy of the armature and/or core is finally dissipated, for example, through friction or in the form of thermal energy.
This cyclic process, also known as chatter or bounce, can have a deleterious effect on the life of the mechanical components of the electrical contactor. Specifically, chatter or bounce can seriously decrease the life of the surfaces at the point of contact, i.e. the lower surface of the armature and the upper surface of the magnetic core.
Additionally, bounce can cause special problems for the electrical components of the contactor. As the armature cyclicly moves towards and away from the magnetic core, the associated electrical circuit may alternatively and repeatedly open and close. At the very least, the periodic opening and closing of the electric circuit will cause unwanted noise within the circuit. Electric arcing occurring between the contacts on the armature and on the housing can also cause the contacts to erode and possibly result in the contacts becoming welded together.
It has been found that bounce in an electric contactor can be controlled by introducing a spring between the magnetic core and the base of the contactor. The spring eliminates the bounce of the armature and associated contacts by dissipating the kinetic energy in the core and the armature. Conventionally, the spring is manufactured separately from the base, as shown in FIG. 2 of U.S. Pat. No. 4,945,328, and is attached to the base during assembly of the contactor.
However, the art of electrical contactor fabrication is well developed and highly competitive. Generally, competitive offerings are comparable in terms of reliability and life with the result that the principal competitive advantage is price. Consequently, it is highly desirable to provide a contactor that is economically manufactured so as to be price competitive while retaining or improving upon the reliability of prior construction.
The present invention is directed to attaining the-above-mentioned result.